As portable telephones come to be used widely, ringtones of portable telephones suddenly ring at a place crowded with many people, for example, in a train or a movie theater, come to be a problem. For people other than the user of the portable telephone, such a ringtone may be annoying.
In order to disable ringtone upon reception of an incoming call, generally, a user manually sets the portable telephone to a manner mode. Techniques for automatically setting the manner mode rather than the manual operation by the user have also been developed.
In the portable telephone described in Patent Document 1, speed of moving of a user holding the portable telephone is estimated based on a time of movement between radio zones of base stations, and based on the result of estimation, whether the user is on a train or not is determined. If it is determined that the user is on a train, the portable telephone is automatically set to a manner mode. If it is determined that the user is not on a train, manner mode is automatically cancelled.
The technique described in Patent Document 2 allows detailed setting of operation modes. By way of example, the following setting is possible. A user puts an RFID (Radio Frequency IDentification) tag in his/her breast pocket. A portable radio terminal detects relative distance and speed between the tag and the portable radio terminal itself, and determines whether the portable radio terminal is taken out from the breast pocket or kept in the pocket. Depending on the result of determination, the terminal is set to a manner mode or the manner mode is cancelled.
According to Patent Document 3, in response to an incoming call from a terminal through a base station, a mobile communication terminal transmits a near field communication signal to other terminals in the near field, and counts the number of responses to the sent communication signal from the other terminals. Based on the number of responses, the mobile communication terminal estimates how many people are in the vicinity thereof. If the number of responses exceeds a prescribed threshold value, the mobile communication terminal notifies the user of the incoming call in the manner mode, and other wise notifies by a ringtone.    Patent Document 1: Japanese Patent Laying-Open No. 2003-61153    Patent Document 2: WO04/107789    Patent Document 3: Japanese Patent Laying-Open No. 2007-221615